Our RV (Winnebago Chalet Class A, 35') came with a 30 amp system and an EMS that allows us to run 2 ACs simultaneously. The ACs are high efficiency and use approx 15 amps (front) and 10 amps (back). Under this setup we cannot run much else. There is a generator switch that allows us to run the back AC on a separate generator circuit so with the generator running, we have up to 45 amps available (30 for coach and 25 for the back AC circuit). The previous owner ran a separate line to the back circuit so that we can simultaneously plug our RV into 30 amps for most things and 15/20 amps for the back AC. It worked well last week in 100+ degree weather and allowed us to do more than run the ACs.